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Fast IP Routing. Axel Clauberg Consulting Engineer Cisco Systems [email protected] Agenda. The Evolution of IP Routing Transmission Update: 10GE Router Architectures So, it‘s all just speed ?. The Evolution of IP Routing. Past. Heard around the corner ?.

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Fast ip routing l.jpg

Fast IP Routing

Axel Clauberg

Consulting Engineer

Cisco Systems

[email protected]


Agenda l.jpg

Agenda

  • The Evolution of IP Routing

  • Transmission Update: 10GE

  • Router Architectures

  • So, it‘s all just speed ?


The evolution of ip routing l.jpg

The Evolution of IP Routing


Heard around the corner l.jpg

Past

Heard around the corner ?

  • IP Routers are slow, sw-based

  • IP Routers cause high latency

  • IP Routers are undeterministic

  • IP Routers do not support QoS


Wan customer access speed evolution l.jpg

WAN Customer Access Speed Evolution

  • Late 1980s: 9.6 Kb/s .. 64 Kb/s

  • Early 1990s:64 Kb/s .. 2 Mb/s

  • Late 1990s:2 Mb/s .. 155 Mb/s

  • Early 2000s:155 Mb/s .. 10 Gb/s


Backbone evolution l.jpg

Late 1980s: 56/64 Kb/s

Early 1990s: 1.5/2 Mb/s

Mid 1990s: 34 Mb/s, 155 Mb/s

Late 1990s: 622 Mb/s, 2,5 Gb/s

Early 2000s: 10 Gb/s, 40 Gb/s

Late 1980s: 10 Mb/s

Early 1990s: 100 Mb/s (FDDI)

Mid 1990s: 155 Mb/s (ATM)

Late 1990s: nx FE, 155 Mb/s, 622 Mb/s, GE

Early 2000s: 10 Gb/s, n x 10 Gb/s

Backbone Evolution

WAN

Campus


Transmission update 10ge l.jpg

Transmission Update: 10GE


Man wan ip transport alternatives l.jpg

MAN/WAN IP Transport Alternatives

IP over ATM

IP over SDH

IP over Optical

IP over Ethernet

GE

10GE

B-ISDN

Multiplexing, Protection and Management at every Layer

IP

IP

ATM

IP

IP

Ethernet

SONET/SDH

ATM

SONET/SDH

IP

Optical

Optical

Optical

Optical

Optical

Lower Cost and Overhead


Ethernet scaling history l.jpg

Ethernet Scaling History

  • 1981: Shared 10 Mbit1x

  • 1992: Switched 10 Mbit10x

  • 1995: Switched 100 Mbit100X

  • 1998: Switched 1 Gigabit1000X

  • 200x: Switched 10 Gigabit 10000X


Moving the decimal point 10 gbe performance and scalability l.jpg

Moving the Decimal Point: 10 GbE Performanceand Scalability

10 Gbps

Ethernet

10 Gbps

STM-64

Gigabit EtherChannel

  • LAN applications

  • Metro applications

  • WAN applications

1 Gbps

Gigabit Ethernet

10 GbE IEEE 802.3ae Standard

Fast EtherChannel

Fast Ethernet

100 Mbps

2001

2002

1996

1997

1998

1999

2000


Why 10 gigabit ethernet l.jpg

Why 10 Gigabit Ethernet

  • Aggregates Gigabit Ethernet segments

  • Scales Enterprise and Service Provider LAN backbones

  • Leverages installed base of 250 million Ethernet switch ports

  • Supports all services (packetized voice and video, data)

  • Supports metropolitan and wide area networks

  • Faster and simpler than other alternatives


Ieee goals for 10 gbe partial list l.jpg

IEEE Goals for 10 GbE(Partial List)

  • Preserve 802.3 Ethernet frame format

  • Preserve minimum and maximum frame size of current 802.3 Ethernet

  • Support only full duplex operation

  • Support 10,000 Mbps at MAC interface

  • Define two families of PHYs

    • LAN PHY operating at 10 Gbps

    • Optional WAN PHY operating at a data rate compatible with the payload rate of OC-192c/SDH VC-4-64c


Ieee 802 3ae task force milestones l.jpg

1999

2000

2001

2002

HSSG

Formed

PAR

Drafted

First

Draft

LMSC

Ballot

Working

Group

Ballot

PAR

Approved

802.3ae

Formed

Standard

IEEE 802.3ae Task Force Milestones

First 10GE deliveries

HSSG= Higher Speed Study Group

PAR= project authorization request

802.3ae= the name of the project and the name of the sub-committee of IEEE 802.3 chartered with writing the 10GbE Standard

Working group ballot= task force submits complete draft to larger 802.3 committee for technical review and ballot

LMSC: LAN/MAN Standards Committee ballot. Any member of the superset of 802 committees may vote and comment on draft


10 gigabit ethernet media goals l.jpg

10 Gigabit Ethernet Media Goals

Media Type

Max Distance

Type

1550 nm Laserextended reach

std/dispersion free fiber

40-100 km

1300 nm Laserstandard reach

single mode fiber

2-10 km

1300 nm LaserCDWM (4x2.5)

multimode fiber

300 m

780 nm VCSELmultichannel

ribbon multimode fiber

200 m


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IEEE Status

  • 802.3ae Meeting 10.-14. Juli 2000

  • 75% Consensus

    • 1550nm Transceiver 40 Km @ SMF

    • 1300nm Transceiver 10 Km @ SMF

  • No Consensus yet

    • Multimode Support

    • 300m mit 62.5µ 160/500 Mhz*Km MM

    • 50µ 2000/500 MHz*Km MM


Router architectures l.jpg

Router Architectures


Components l.jpg

Components

  • Memory Architecture

  • Interconnect

  • Forwarding Engine

  • Scalability

  • Stability

  • Queueing / QoS


Basic design l.jpg

Basic Design

Router

Buffer

Memory

Interfaces

...

...

Inputs

Outputs

  • Data are of random sizes

  • Arrival is async, unpredictable, independantly on i/f

  • Data have to be buffered

  • TCP/IP traffic is bursty, but short-term congestion only

Forwarding

Engine

Route

Processor


How much buffers l.jpg

How much buffers ?

  • Rule of Thumb: RTT x BW

    (Villamizer & Song, High Performance TCP in ANSNET, 1994)

  • STM-16 @ 200 ms: ~ 60 MB buffering capacity


How to buffer l.jpg

How to Buffer ?

  • SRAM

    • Fast, Power-hungry, Density 8 Mb -> 16 Mb, Simple Controller Design

  • DRAM / SDRAM

    • Slower, Less Power, Density 64 Mb -> 256 Mb, Complex Controller Design


Interconnect l.jpg

Interconnect

  • Switch Fabric / Crossbar

  • Shared Memory

  • Variations


Switch fabric crossbar l.jpg

Ingress Line Cards

Egress Line Cards

Line

Card 0

Line

Card 0

Switch

Fabric

Line

Card 1

Line

Card 1

Scheduler

Line

Card N

Line

Card N

RP

RP

Switch Fabric / Crossbar

  • Packet forwarding decision done on each linecard

  • Ingress and Egress Buffering on Linecards

  • Possible Problem: Head of Line Blocking

  • Solution: VOQ


Linecard in detail l.jpg

Physical

Layer

(Optics)

Layer 3

Engine

Fabric

Interface

To Fabric

RX

Switch

Fabric

CPU

From Fabric

TX

Scheduler

Linecard in Detail

  • HOL Blocking can occur when packet cannot flow off transmit linecard

  • Packet will be buffered on receiving linecard

  • Packet blocks other packets to other linecards

  • Solution: Virtual Output Queues, one per egress linecard


Gsr queuing architecture l.jpg

GSR Queuing Architecture

Input

Ports

Transmit

Line Card

Output

Ports

Receive Line Card

Virtual

Output

Queues

Group of 8 CoS

Queues

Per Interface

(M-DRR)

Crossbar Switch Fabric

W-RED

DRR

CAR

CEF


Shared memory architecture physically centralized l.jpg

Shared Memory ArchitecturePhysically Centralized

  • One large memory system, data passing through it

  • Simple memory management

  • High speed memory

  • Simple Linecards

  • Needs SRAM for high speeds

Line Cards 1-8

Interconnects

&

Forwarding

Engine

2.5Gbps

2.5Gbps

40

G

Memory Controller

2.5Gbps

2.5Gbps


Shared memory architecture distributed l.jpg

Line Cards 1-8

2.5Gbps

2.5Gbps

2.5Gbps

2.5Gbps

Memory

System

Memory

System

Shared Memory ArchitectureDistributed

  • Memory distributed over linecards

  • Memory controller treats sum of pieces as shared memory

  • Packet forwarding decision in central engine(s)

  • Difficult to maximize interconnect efficiency

    • Egress line cards simply request packets from shared memory

    • Causes Head of Line (HOL) blocking and high latency, worsening under moderate-to-heavy system load or with multicast traffic

Memory

Controller

&

Forwarding

Engine(s)


Switch fabric vs shared memory l.jpg

Switch Fabric vs. Shared Memory

  • Shared Memory requires only half the buffer space

  • HOL Blocking in Shared Memory, especially for Multicast

  • Involvement of distributed shared memory causes more points of failure


Forwarding engine l.jpg

Forwarding Engine

  • Classifying the packet

    • IPv4, IPv6, MPLS, ...

  • Packet validity (TTL, length, ...)

  • Next Hop

  • Basic Statistics

  • Optional:

  • Policing, Extended Statistics, RPF check (security, Multicast), QoS, Tunnel, ...

  • Distributed vs. Central


Central forwarding l.jpg

Central Forwarding ?

  • IP Longest match

    • Hash vs. TCAM vs. Tree Lookup

  • Tree Lookup requires high number of routing table lookups

    • Need SRAM

    • Danger to run out of SRAM

    • Forwarding speed dependant on depth of routing table


Distributed forwarding l.jpg

Distributed Forwarding

  • One copy of forwarding info per linecard

  • Parallel processing without sync or communication between linecards

  • Able to use TCAMs and SDRAMs


So it s all just speed l.jpg

So, it’s all just speed ?


So it s just speed l.jpg

So, it’s just speed ?

  • Services

    • IP Multicast

    • IP QoS

    • Security

  • IPv6

  • MPLS

  • Manageability

  • Availability

  • Investment protection


Multicast solutions end to end architecture l.jpg

End Stations (hosts-to-routers):

IGMP

Switches (Layer 2 Optimization):

IGMP Snooping

Routers (Multicast Forwarding Protocol):

PIM Sparse Mode

Multicast routing across domains

MBGP

Multicast Source Discovery

MSDP with PIM-SM

ISP A

ISP B

MSDP

RP

Multicast Source

Y

Multicast Source

X

DR

RP

ISP B

ISP A

MBGP

CGMP

DR

PIM-SM

IGMP

DR

Multicast SolutionsEnd-to-End Architecture

Interdomain Multicast

Campus Multicast


Summary l.jpg

Summary

  • IP Routers have evolved during the past years

  • Line rate up to 10 Gb/s

  • Crossbar architectures with distributed forwarding seem to scale better than shared memory architectures

  • Services remain the most decisive factor


Outlook l.jpg

Outlook

  • 10 Gb/s Interfaces supported in 2000

    • 10GE, STM-64/OC-192

  • High density of 10 Gb/s interfaces soon in a PoP

  • Next step will be STM-256/OC-768 = 40 Gb/s

  • Will these routers be „Palm-Size“ ?

    • Probably not...


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